1528-58-1Relevant articles and documents
Visible-light promoted oxidative cyclization of cinnamic acid derivatives using xanthone as the photocatalyst
Zhao, Bin,Xu, Bo
supporting information, p. 568 - 573 (2021/02/06)
We have developed an efficient photocatalytic synthesis of coumarin derivativesviaa tandem double bond isomerization/oxidative cyclization of cinnamic acids. Inexpensive and stable xanthone was used as the photocatalyst, and readily available Selectfluor was used as the oxidant. This method tolerates a wide range of functional groups and offers excellent chemical yields in general. Besides, the photocatalytic oxidative cyclization of cinnamic acid esters gives dimerized lignan-type products.
Carbene-Catalyzed α,?-Deuteration of Enals under Oxidative Conditions
Chen, Qiao,Chi, Yonggui Robin,Jin, Zhichao,Li, Shaoyuan,Song, Runjiang,Tian, Weiyi,Xu, Jun,Zhang, Xiaolei
, p. 5475 - 5482 (2020/08/25)
Organic compounds with deuterated allyl groups are very attractive for drug entities to enhance pharmacokinetic properties, since allylic C-H bonds are prone to metabolic oxidation and the deuterated versions can be less prone to such metabolism. However, direct deuteration at allylic C-H moieties is still a challenge. Few examples have been reported by transition-metal catalysis and no such reports have been documented in an organocatalytic fashion. Herein, a carbene-catalyzed C-H deuteration of enal at allylic C(sp3) and C(sp2) centers is disclosed. Addition of the carbene catalyst to the aldehyde moiety of enals to eventually activate the α- A nd ?-carbon atom under oxidative conditions is critical to achieve high deuterium incorporation. Key mechanistic steps of our reaction include carbene catalyst addition, azolium ester formation, remote ?-carbon activation, reversible α- A nd ?-carbon enolization, and iterative H/D exchanges. The reaction is performed under mild conditions using D2O as the deuterium source to efficiently afford α,?-deuterated 2-alkenoic acids and their derivatives in good to excellent yields and high deuterium incorporation. These labeled products containing carbonyl and allyl bifunctionalities are valuable building blocks for further transformations, eventually leading to otherwise challenging labeled targets including deuterated allylic derivatives, aliphatic derivatives and polydeuterated drugs (e.g., Ibuprofen). The convenient and scalable synthesis has application potential for materials and pharmaceuticals.
Copper-Photocatalyzed Contra-Thermodynamic Isomerization of Polarized Alkenes
Bouillon, Jean-Philippe,Brégent, Thibaud,Poisson, Thomas
, p. 7688 - 7693 (2020/10/09)
The contra-thermodynamic isomerization of α- and β-substituted cinnamate derivatives catalyzed by the Cu(OAc)2/rac-BINAP complex under blue light irradiation is reported. The use of an oxazolidinone template, which favored the complexation of the copper catalyst to the substrate, allowed the E → Z isomerization of the catalytically formed chromophore under simple and robust reaction conditions in good to excellent ratios. The mechanism of this process based on the transient formation of a chromophore was also studied.
Enantioselective epoxidation of β,β-disubstituted enamides with a manganese catalyst and aqueous hydrogen peroxide
Clarasó, Carlota,Vicens, Laia,Polo, Alfonso,Costas, Miquel
, p. 2430 - 2435 (2019/03/29)
Enantioselective epoxidation of β,β-disubstituted enamides with aqueous hydrogen peroxide and a novel manganese catalyst is described. Epoxidation is stereospecific and proceeds fast under mild conditions. Amides are disclosed as key functional groups to enable high enantioselectivity.
Pd(II)/Bipyridine-Catalyzed Conjugate Addition of Arylboronic Acids to α,β-Unsaturated Carboxylic Acids. Synthesis of β-Quaternary Carbons Substituted Carboxylic Acids
Liu, Rui,Yang, Zhenyu,Ni, Yuxin,Song, Kaixuan,Shen, Kai,Lin, Shaohui,Pan, Qinmin
, p. 8023 - 8030 (2017/08/14)
Pd(II)/bipyridine-catalyzed conjugate addition of arylboronic acids to α,β-unsaturated carboxylic acids (including β,β-disubstituted acrylic acids) was developed and optimized, which provided a mild and convenient method for the highly challenging synthesis of β-quaternary carbons substituted carboxylic acids.
One Photocatalyst, n Activation Modes Strategy for Cascade Catalysis: Emulating Coumarin Biosynthesis with (-)-Riboflavin
Metternich, Jan B.,Gilmour, Ryan
supporting information, p. 1040 - 1045 (2016/02/05)
Generating molecular complexity using a single catalyst, where the requisite activation modes are sequentially exploited as the reaction proceeds, is an attractive guiding principle in synthesis. This requires that each substrate transposition exposes a catalyst activation mode (AM) to which all preceding or future intermediates are resistant. While this concept is exemplified by MacMillan's beautiful merger of enamine and iminium ion activation, examples in other fields of contemporary catalysis remain elusive. Herein, we extend this tactic to organic photochemistry. By harnessing the two discrete photochemical activation modes of (-)-riboflavin, it is possible to sequentially induce isomerization and cyclization by energy transfer (ET) and single-electron transfer (SET) activation pathways, respectively. This catalytic approach has been utilized to emulate the coumarin biosynthesis pathway, which features a key photochemical E → Z isomerization step. Since the ensuing SET-based cyclization eliminates the need for a prefunctionalized aryl ring, this constitutes a novel disconnection of a pharmaceutically important scaffold.
Enantioselective Hydrogenation of β,β-Disubstituted Unsaturated Carboxylic Acids under Base-Free Conditions
Yan, Qiaozhi,Kong, Duanyang,Zhao, Wei,Zi, Guofu,Hou, Guohua
, p. 2070 - 2077 (2016/03/15)
An additive-free enantioselective hydrogenation of β,β-disubstituted unsaturated carboxylic acids catalyzed by the Rh-(R,R)-f-spiroPhos complex has been developed. Under mild conditions, a wide scope of β,β-disubstituted unsaturated carboxylic acids were hydrogenated to the corresponding chiral carboxylic acids with excellent enantioselectivities (up to 99.3% ee). This methodology was also successfully applied to the synthesis of the pharmaceutical molecule indatraline.
A Bio-Inspired, Catalytic e → Z Isomerization of Activated Olefins
Metternich, Jan B.,Gilmour, Ryan
, p. 11254 - 11257 (2015/09/21)
Herein, Natures flavin-mediated activation of complex (poly)enes has been translated to a small molecule paradigm culminating in a highly (Z)-selective, catalytic isomerization of activated olefins using (-)-riboflavin (up to 99:1 Z/E). In contrast to the prominent Z → E isomerization of the natural system, it was possible to invert the directionality of the isomerization (E → Z) by simultaneously truncating the retinal scaffold, and introducing a third olefin substituent to augment A1,3-strain upon isomerization. Consequently, conjugation is reduced in the product chromophore leading to a substrate/product combination with discrete photophysical signatures. The operationally simple isomerization protocol has been applied to a variety of enone-derived substrates and showcased in the preparation of the medically relevant 4-substituted coumarin scaffold. A correlation of sensitizer triplet energy (ET) and reaction efficiency, together with the study of additive effects and mechanistic probes, is consistent with a triplet energy transfer mechanism.
Effect of multinuclear copper/aluminum complexes in highly asymmetric conjugate addition of trimethylaluminum to acyclic enones
Endo, Kohei,Hamada, Daisuke,Yakeishi, Sayuri,Shibata, Takanori
supporting information, p. 606 - 610 (2013/02/23)
Al and friends: Asymmetric conjugate addition of Me3Al to β,β-disubstituted α,β-unsaturated ketones in the presence copper and L1 leads to a highly efficient construction of an all-carbon-substituted chiral quaternary center. This result is the first example of an asymmetric conjugate addition of Me3Al to acyclic enones to give a chiral quaternary carbon center with excellent yield and enantioselectivity under mild reaction conditions. Copyright
Direct competitive enzyme-linked immunosorbent assay for the determination of the highly polar short-chain sulfophenyl carboxylates
Estevez, M.-Carmen,Galve, Roger,Sanchez-Baeza, Francisco,Marco, M.-Pilar
, p. 5283 - 5293 (2008/02/02)
A direct enzyme-linked immunosorbent assay for the detection of the short-chain sulfophenylcarboxylic acids (SPCs), the main metabolites of the linear alkylbenzene-sulfonates, is reported. Six SPCs (2C3, 2C 4, 3C4, 2C
